1. Technical Field to which the Invention Pertains
The present invention relates to a washing liquid and, in particular, it relates to a washing liquid for removing particulate contaminants adsorbed on the surface of a hydrophobic substrate such as bare silicon or a low-permittivity (Low-K) film.
Furthermore, the present invention relates to a washing liquid used in the washing of, in particular, a substrate subsequent to chemical-mechanical polishing (hereinafter, called CMP) in a semiconductor production process.
2. Prior Art
Accompanying the increasing integration of ICs, there is a demand for strict contamination control since trace amounts of impurities greatly influence the performance and yield of a device. That is, strict control of particles and metals on a substrate is required, and various types of washing liquids are therefore used in each of the semiconductor production processes.
With regard to washing liquids generally used for semiconductor substrates, there are sulfuric acid-aqueous hydrogen peroxide solution, ammonia water-aqueous hydrogen peroxide solution-water (SC-1), hydrochloric acid-aqueous hydrogen peroxide solution-water (SC-2), dilute hydrofluoric acid, etc., and the washing liquids are used singly or in combination according to the intended purpose. In recent years, CMP technique has been introduced into such semiconductor production processes as planarization of an insulating film, planarization of a via-hole, and damascene wiring. Generally, CMP is a technique in which a film is planarized by pressing a wafer against a cloth called a buff and rotating it while supplying a slurry, which is a mixture of abrasive particles, a chemical agent and water, so that an interlayer insulating film material or a metal film material is polished by a combination of chemical and physical actions. Because of this, the CMP-treated substrate is contaminated with large amounts of particles and metals including alumina particles and silica particles used in the abrasive particles. It is therefore necessary to employ cleaning to completely remove these contaminants prior to the following process. As a post-CMP washing liquid, an alkali aqueous solution such as ammonia water is conventionally used for removing particles. For removing metallic contaminants, techniques using an aqueous solution of organic acid and a complexing agent have been proposed in JP, A, 10-72594 and JP, A, 11-131093. As a technique for simultaneously removing metallic contaminants and particulate contaminants, a washing aqueous liquid in which an organic acid and a surfactant are combined has been proposed in JP, A, 2001-7071.
One of the fields in which CMP is applied is the planarization of an interlayer insulating film. The interlayer insulating film is mainly formed from an SiO2-based film, and since in this technique a metallic material is not exposed, conventionally, washing with an aqueous solution of ammonium fluoride or an aqueous solution of the organic acid described above can be employed. In recent years Cu has been used as a wiring material in order to increase the response speed of semiconductor devices, and at the same time there have been attempts to use as the interlayer insulating film an organic film such as an aromatic aryl polymer, a siloxane film such as MSQ (Methyl Silsesquioxane) or HSQ (Hydrogen Silsesquioxane), an SiOC film, a porous silica film, etc., which have lower permittivity than that of the conventional SiO2-based film. These novel materials cannot be washed satisfactorily by using conventional washing liquids as they are. Furthermore, there are cases, not only in the planarization of interlayer insulating films, but also in the planarization of Cu wiring, which is another field of application of CMP, in which the above-mentioned low permittivity film is exposed due to overpolishing, and since in these cases also conventional washing liquids cannot be used satisfactorily for washing, there is a desire for a washing liquid that is effective for these semiconductor substrates.